Metallurgical furnace

ABSTRACT

An electrode seal for use in a metallurgical furnace, the furnace comprising a furnace space heated by electrodes extending through an aperture into the furnace space. The electrode seal comprises at least three sets of shoes in consecutive lateral contact, each shoe having a biasing member for biasing a surface of the shoe toward one of the electrodes thereby allowing the one electrode to longitudinally move within the electrode seal while providing electrical insulation between the electrode and the aperture.

CROSS-REFERENCE

This application is a continuation of U.S. patent application Ser. No.14/575,928 filed Dec. 18, 2014, which is a continuation in part of PCTapplication serial no. PCT/CA2013/001086, filed Dec. 20, 2013, both ofwhich are incorporated herein by reference in their entirety.

TECHNICAL FIELD

This invention generally relates to metallurgical furnaces, and, moreparticularly, to electrical metallurgical furnaces.

BACKGROUND

Several forms of metallurgical furnace having a refractory, an outersteel shell surrounding the refractory, a roof, and a hearth are knownin the art. Furnaces known in the art may be rectangular or square inhorizontal section (when viewed from above or below), or may be round inhorizontal section. Furnaces known in the art generally have a metalstructure supported by the hearth and protected by the refractory, inwhich metal, slag, and other materials are to be heated. Above theheated metal and slag is an area of space referred to as “freeboard”,which is surrounded horizontally by the refractory. An electricalmetallurgical furnace uses electricity for heating and melting. Moreparticularly, in the typical round electrical metallurgical furnace,three electrodes are used to produce electric arcs for heating thecontents of the hearth. In the typical electrical furnace, therefractory is typically made of stacked bricks.

The brick refractory typically serves to provide thermal insulationbetween different elements inside the furnace, including molten metaland slag as well as heated gas in the inner furnace space, from thesurrounding environment. In furnaces known in the art, the temperatureof the molten material may range from 1400 to 2200 degrees Celsius. Inuse, the inner surface of the brick refractory may be coated with asolid layer of “frozen” slag or deposited fumes and dusts, also referredto as a “skull”, which layer may be heated to a temperature in excess of1000 degrees Celsius. The thickness of this “skull” will vary dependingon the furnace power level and arc length, which is a function ofvoltage.

In some furnaces known in the art, gaps between the bricks of the brickrefractory and cracks within the bricks tend to form over time and use,especially over the course of repeated heating and cooling cycles due tothermal stresses. Further, the brick refractory may be corroded ordegraded due to chemical, thermal, and mechanical stresses caused by theproperties of the molten metal and slag contained therein, resulting ineventual breakdown of the refractory from within. Gaps and cracks in therefractory may result in escape of molten metal from the furnace, intothe brickwork of the refractory. Wearing down and breaking of the bricksmay ultimately result in failure of the refractory. The risk of leakthrough the skull and then through spaces in the refractory, andeventually out of the furnace, is increased by the gaps between thebricks of the refractory.

In some furnaces known in the art, the roof fails to provide adequatethermal insulation for the surrounding environment. The roof may furtherfail to provide a barrier to prevent the escape of toxic gases,including carbon monoxide, into the surrounding environment, creating apotentially hazardous environment for workers.

In some electric furnaces known in the art, the high temperature createdby the electrodes may unduly heat the roof. Additionally, the highvoltage running through the electrodes may cause risk of electrocutionfor workers working near the roof.

The present invention generally addresses certain drawbacks ofmetallurgical furnaces known in the art.

SUMMARY

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

In some embodiments, the present invention seeks to provide ametallurgical furnace having a refractory with an expandable segmentedouter steel shell, to allow the refractory to expand and contract withthermal cycling of the furnace. In some embodiments, the presentinvention seeks to provide a metallurgical furnace having a verticalcompression member in communication with the refractory, to allow therefractory to expand and contact vertically with thermal cycling of thefurnace. In some other embodiments, the present invention seeks toprovide a metallurgical furnace having an insulated roof. In somefurther embodiments, the present invention seeks to provide isolation ofthe electrodes. In some additional embodiments, the present inventionseeks to provide external cooling of a furnace. While there existssynergies between the various exemplary embodiments, the embodiments areexpected to work with other conventional furnace designs (e.g.,conventional brick refractory and/or electrode and/or external coolingsystem and/or roof designs).

In a first broad aspect, the present invention provides a metallurgicalfurnace having a refractory, surrounding a furnace space, fordissipating heat when the furnace space is heated, and a force exertingmember for contracting a segmented outer shell around the refractory,toward the furnace space, as the refractory contracts when the furnacespace is cooling.

The force exerting member may allow the refractory to expand when thefurnace space is heated and may exert a compressive force on therefractory as the refractory contracts when the furnace space iscooling. The force exerting member may have at least one cable disposedaround an outer surface of the segmented outer shell, and may have aplurality of cable pairs disposed at interval around an outer surface ofthe segmented outer shell. The cables may have a tension member mountedthereto for adjusting the length of the cable, thereby adjusting thetension of the tension member and the force exerted by the cable.

In another aspect, the force exerting member may be a plurality ofpressing members disposed around an outer surface of the segmented outershell, each pressing member for pressing against the outer surface andthereby exerting a compressive force thereon. The pressing members maybe spring members, may be biased against the outer surface of thesegmented steel shell by biasing members, and may be adjustable to applygreater or lesser compressive force on the segmented outer shell.

In another aspect, the furnace may have at least one tension member,which may be a spring, mounted to the force exerting member for exertingtension on the force exerting member, thereby exerting the compressiveforce. The force exerting member may be supported on at least onesupport member, or may be supported on a plurality of support memberswhich may be vertical columns, for example buckstay columns, disposedaround the segmented outer shell. The positioning member may allow formovement of the segmented outer shell relative to the force exertingmember. The force exerting member may engage at least one positioningmember, and the positioning member may be a wheel member pivotallymounted to the support member.

In another aspect, the furnace may have at least one force adjustmentmember connected to the force exerting member, for initially adjustingthe force exerted by the force exerting member. At least one forcemeasuring member may be connected to the tension member, which may be adynamometer for measuring the tension of a spring, for measuring thetension of the tension member and thereby measuring the force exerted bythe force exerting member.

In another aspect, the refractory may be radially symmetric incross-section at at least one point along its height, and may begenerally round in cross-section at at least one point along therefractory's height. The segmented outer shell may be generallycylindrical in shape in a contracted configuration when the furnacespace is cooled, and may have at least one gap between horizontallyadjacent shell segments in an expanded configuration when the furnacespace is heated.

In another aspect, the furnace may have one or more sealing members forsealing a gap between horizontally adjacent shell segments in anexpanded configuration when the furnace space is heated. The sealingmembers may be strips for placement between the refractory and the outershell at a position for sealing at least one gap between horizontallyadjacent shell segments in an expanded configuration when the furnacespace is heated.

In another aspect, the refractory may have an innermost layer ofthermally conductive bricks disposed around the furnace space forabsorbing and dissipating the heat. The refractory may also have atleast one additional layer of thermally conductive bricks disposedaround the innermost layer of thermally conductive bricks, for furtherabsorbing and dissipating heat. The additional layer may include bricksmade of a different material than bricks of innermost layer. Some of thethermally conductive bricks may include a periclase material. Therefractory may also have an outermost layer of bricks disposed aroundthe one or more layers of thermally conductive bricks, which may be madeof a graphite material.

In another aspect, prior to the furnace space being initially heated,the furnace may have at least one layer of spacer material between theinnermost and the least one additional layer of thermally conductivebricks, thereby resulting in a refractory diameter larger than acontracted configuration of the shell. The spacer material may be madeof a material adapted to combust or dissipate when the furnace space isheated, thereby leaving space to compensate for additional spaceoccupied by expanding thermally conductive bricks.

In another aspect, the segmented outer shell of the furnace may have atleast three segments, may have a smaller or larger number of segmentsproportionate with the relative size of the furnace, and may have eightor more segments. Each segment of the segmented outer shell may have anedge which is adapted to cooperate with an edge of an adjacent shellsegment.

In another aspect, the furnace may have one or more sealing members forplacement between the segmented outer shell and the refractory, eachsealing member for sealing one or more gaps formed between horizontallyadjacent shell segments in an expanded configuration when the furnacespace is heated.

In another aspect, the furnace may have one or more retaining membersfor movably connecting pairs of horizontally adjacent shell segments,each retaining member thereby providing a maximum gap distance betweeneach connected pair of horizontally adjacent shell segments.

In a second broad aspect, the present provides a method of adapting ametallurgical furnace having a refractory surrounding an inner furnacespace for dissipating heat when the furnace space is heated, and havinga contiguous outer shell surrounding the refractory. The method mayinclude the steps of dividing the outer shell into a segmented outershell, and disposing at least one force exerting member around therefractory, the force exerting member for contracting the segmentedouter shell, toward the furnace space, as the refractory contracts whenthe furnace space is cooling.

In another aspect, the force exerting member may allows the refractoryto expand when the furnace space is heated, and may exert a compressiveforce on the refractory as the refractory contracts when the furnacespace is cooling. The force exerting member may include a cable disposedaround an outer surface of the segmented outer shell.

In another aspect, the method may include a step of replacing therefractory with at least one inner layer of thermally conductive brickssurrounding the inner furnace space, and with at least one outer layerof bricks surrounding the one or more inner layers. The inner layer mayinclude periclase, alumina, silica or chrome-based bricks, and the outerlayer may include graphite bricks

In another aspect, the method may include a step of mounting at leastone tension member, which may be a spring, to the force exerting memberfor maintaining the force exerting member under tension.

In another aspect, the method may include a step of supporting the forceexerting member on at least one support member, which may be a verticalcolumn, disposed around the segmented outer shell.

In another aspect, the method may include a step of engaging the forceexerting member with at least one positioning member, the positioningmember for allowing movement of the segmented outer shell relative tothe force exerting member. The positioning member may be a wheel memberpivotally mounted to the vertical column.

In another aspect, the method may include a step of connecting at leastone force adjustment member to the force exerting member for adjustingthe force exerted by the force exerting member. The method may furtherinclude a step of adjusting the length of the force exerting member withthe force adjustment member, thereby adjusting the tension of thetension member and the force exerted by the cable, and may also includea step of connecting at least one force measuring member to the tensionmember and measuring the force exerted by the force exerting member.

In another aspect, where the force exerting member includes a cable andthe force adjustment member is for adjusting the length of the cable,thereby adjusting the tension of the tension member and thus the forceexerted by the cable, the force measuring member may be a dynamometer,for measuring the force exerted by the cable.

In another aspect, the method may include a step of disposing at leastone layer of spacer material between the thermally conductive bricks ofthe same layer of refractory, thereby resulting in a diameter of therefractory larger than a contracted configuration of the shell, whereinthe spacer material includes a material adapted to combust or dissipatewhen the furnace space is heated, thereby leaving space to compensatefor additional space occupied by expanding thermally conductive bricks.

In another aspect, the method may include a step of dividing the outershell into at least three segments, at least eight segments, and/or intoa smaller or larger number of segments proportionate with the relativesize of the furnace.

In another aspect, the method may include a step of providing one ormore sealing members between the segmented outer shell and therefractory, each sealing member for sealing one or more gaps formedbetween horizontally adjacent shell segments in an expandedconfiguration when the furnace space is heated.

In another aspect, the method may include a step of movably connectingone or more pairs of horizontally adjacent shell segments, therebyproviding a maximum gap distance between each connected pair ofhorizontally adjacent shell segments.

In a third broad aspect, the present provides a force exerting memberfor use in a metallurgical furnace having a refractory, surrounding afurnace space of the furnace, for dissipating heat when the furnacespace is heated. The force exerting member has a surrounding structurefor surrounding a segmented outer shell around the refractory, and hasat least one tension member, which may be a spring and which may beconnected to an initial tension adjuster for initially adjusting theforce exerted by the force exerting member, for exerting force on thesurrounding structure for contracting the segmented outer shell aroundthe refractory, toward the furnace space, as the refractory contractswhen the furnace space is cooling.

In another aspect, the initial tension member is for adjusting the forceexerting member's length. The force exerting member may be mounted to aforce adjustment member, which may be a dynamometer, for measuring theforce exerted by the force exerting member.

In a fourth broad aspect, the present invention provides a metallurgicalfurnace including a refractory, which may be made of a plurality ofbricks surrounding the furnace space, surrounding a furnace space fordissipating heat when the furnace space is heated and a verticalcompression member exerting a compressive force upon the refractory,thereby vertically compressing the refractory as the refractorycontracts when the furnace space is cooling. The vertical compressionmember(s) may be one or more springs.

In another aspect, the vertical compression member may be further forallowing expansion of the refractory expands when the furnace space isheated.

In another aspect, the refractory may include a first layer of brickssurrounding the furnace space and a second layer of bricks surroundingthe first layer of bricks.

In another aspect, the furnace may include one or more force transfermembers for transferring the force exerted by the vertical compressionmember to one or more of the bricks in the layers. The force transfermember may be a covering member for transferring the force exerted to alayer of bricks.

In another aspect, the first layer of bricks may not be anchored to thesecond layer of bricks.

In another aspect, the vertical compression member may include a forceadjusting member for adjusting the force exerted thereby. The verticalcompression member may also be mounted to a suspension member, which inturn may be mounted to a supporting member. The suspension member may bemovably mounted to the supporting member, to permit movement of thesuspension members to accommodate contraction and/or expansion of therefractory. The furnace may also include one or more length adjustingmembers for adjusting the length of each suspension member, therebyadjusting the force exerted by the vertical compression member.

In another aspect, the refractory is adapted to compensate for a greaterexpansion of an inner portion of the refractory as compared with that ofan outer portion of the refractory when the refractory is heated by thefurnace space. The refractory may include at least one layer of brickssurrounding the refractory, and the layer of bricks may include at leastone brick having a greater vertical height on an outer face as comparedwith that of an inner face, to compensate for the greater expansion ofthe inner face as compared with that of the outer face when the brick isheated by the furnace space.

In a fifth broad aspect, the present invention provides a method ofadapting a metallurgical furnace including a refractory, the refractorysurrounding a furnace space and for dissipating heat when the furnacespace is heated and optionally including a plurality of brickssurrounding the furnace space. The method includes a step of disposing avertical compression member against the refractory for verticallycompressing the refractory as the refractory contracts when the furnacespace is cooling and/or for accommodating for vertical expansion of therefractory when the furnace is heating. The refractory may include afirst layer of bricks surrounding the furnace space and a second layerof bricks surrounding the first layer of bricks.

In another aspect, the method may include a step of disposing one ormore force transfer members between the vertical compression member andthe refractory, the force transfer member, which may be a coveringmember for transferring the force to at least one of the layers ofbricks, and is for transferring force exerted by the verticalcompression member, which may be a spring, to one or more of the bricksin the layers.

In another aspect, the first layer of bricks may not be anchored to thesecond layer of bricks.

In another aspect, the vertical compression member may include a forceadjusting member for adjusting the force exerted.

In another aspect, the method may include a step of mounting thevertical compression member to a suspension member, which may in turn bemounted to a supporting member.

In another aspect, the method may include a step of movably mounting thesuspension member to the supporting member, to thereby permit movementof the suspension members to accommodate at least one of contraction orexpansion of the refractory.

In another aspect, the method may include a step of mounting one or morelength adjusting members to the suspension member, and adjusting thelength of the suspension member with the length adjusting member,thereby adjusting the force exerted by the vertical compression member.

In another aspect, the method may include a step of adapting therefractory to compensate for greater expansion of an inner portion ofthe refractory as compared with that of an outer portion of therefractory when the refractory is heated by the furnace space.

In another aspect, the method may include a step of adapting at leastone brick in the refractory to have a greater vertical height on anouter face as compared with that of an inner face, to compensate forgreater expansion of the inner face as compared with that of the innerface when the brick is heated by the furnace space.

In a sixth broad aspect, the present invention provides a system forcooling a metallurgical furnace, the system including an outer sleevesurrounding a layer of air heated by an inner furnace space of thefurnace, and including one or more air displacement members fordisplacing the heated surrounding air away from the furnace.

In another aspect, the displacement member may be for drawing cooler airinto the outer sleeve by displacing the heated surrounding air away fromthe furnace.

In another aspect, cooler air may be drawn into the outer sleeve by theone or more air displacement members.

In another aspect, the heated surrounding air may be drawn away from thefurnace by the one or more air displacement members.

In another aspect, the outer sleeve may include one or more aperturesfor allowing air to pass therethrough.

In another aspect, the system may include one or more spray nozzles forspraying liquid coolant, from within the layer of air, toward an outersurface of the furnace. The spray nozzles may include an atomizer foratomizing the liquid coolant into a mist and for spraying the misttoward the outer surface of the furnace.

In another aspect, the system may include a monitor for monitoringaccumulation of liquid coolant.

In another aspect, the system may include a regulator for reducing aliquid coolant spraying rate in response to accumulation of liquidcoolant.

In another aspect, the outer sleeve may include a plurality of sleevesegments. Each sleeve segment may corresponds with a segment of a steelshell surrounding a refractory of the metallurgical furnace, and eachsleeve segment and corresponding shell segment may be for collectivelysurrounding a volume of heated air from the layer of air to be displacedaway from the furnace.

In a seventh broad aspect, the present invention provides a method ofcooling a metallurgical furnace, including the steps of displacing airheated by an inner furnace space of the furnace away from the furnacewith one or more air displacement members, the heated air beingsurrounded by an outer sleeve thereby forming a layer of heated airsurrounding the furnace.

In another aspect, the method may include a step of spraying coolingliquid, from within the layer of air, toward the outer surface of thefurnace.

In another aspect, the method may include a step of atomizing thecooling liquid to be sprayed toward the outer surface of the furnace.

In another aspect, the method may include a step of regulating thespraying of the cooling liquid in response to detected levels of coolingliquid at a lower surface of the furnace.

In another aspect, the outer sleeve may include a plurality of sleevesegments. Each sleeve segment may correspond with a segment of a steelshell surrounding the refractory of the metallurgical furnace, eachsleeve segment and corresponding shell segment being for collectivelysurrounding a volume of heated air from the layer of air to be displacedaway from the furnace.

In an eighth broad aspect, the present invention provides a roof for ametallurgical furnace, including a roof member having suspension membersextending through an outer surface, the suspension members supporting aninner mesh of the roof member, the inner mesh supporting insulatingmaterial, which may be castable, and which may be non-conductive, and/ora thermal insulating material, and/or which may be non-reactive withwater. The insulating material may be a high alumina castable material,the insulating material has a thickness of greater than 40 cm.

In another aspect, the outer surface may form an open ended externalcopper cap.

In another aspect, the roof may include a plurality of roof membersdimensioned to fit together to form the roof.

In another aspect, the upper surface of the roof may be dimensioned toallow liquid coolant dispersed thereon to flow outwardly toward aperiphery of the roof, and may be dimensioned to contain a layer of theliquid coolant thereon. The liquid coolant may be for cooling the roofand/or for providing a liquid seal on the roof to prevent gas escapefrom an inner space of the furnace.

In another aspect, the roof may include a contiguous trough forcontaining the liquid coolant, thereby allowing formation of the layerof the liquid coolant having a target depth to form on the upper surfaceof the roof. The trough may include an outer wall that is higher than aninner wall, to allow the formation of the layer of the liquid coolanthaving the target depth to form on the upper surface of the roof.

In another aspect, the roof may include a framework supported by thesuspension members, the framework supporting the inner mesh. Theframework may be made partly or entirely of rebar, and the inner meshmay be made partly or entirely of steel mesh.

In another aspect, the roof may include a pump for dispersing and/orcirculating the liquid coolant onto the roof.

In another aspect, the roof may include an elastic member formaintaining a seal between the roof and an upper surface of themetallurgical furnace.

In another aspect, at least one gap between adjacent roof members of theplurality of roof members may be sealed with a sealant, which may becement, tar, high temperature silicon sealant, or any combinationthereof, to prevent flow of fluids through the gap.

In another aspect, the roof may include at least one opening toaccommodate at least one feed pipe.

In another aspect, the roof may include a copper cylinder extending intothe furnace space at one end and extending beyond a target liquidcoolant height at a second end, the copper cylinder surrounding the feedpipe and sealingly joined thereto.

In a ninth broad aspect, the present invention provides a metallurgicalfurnace for smelting minerals including a refractory, surrounding afurnace space, for dissipating heat when the furnace space is heated.The refractory includes an inner layer having a heat dissipationthickness, and the inner layer include a first plurality of bricks of afirst type having the heat dissipation thickness, and a second pluralityof bricks of a second type having a sacrificial thickness greater thanthe heat dissipation thickness, the second plurality of bricksprotruding towards the furnace space. The sacrificial thickness may bedetermined from a predictable consistency of molten slag formed duringuse of the metallurgical furnace for smelting minerals, and may bedetermined from a predictable consistency of the molten metal during useof the metallurgical furnace for smelting minerals.

In another aspect, the sacrificial thickness may vary along the heightof the refractory according to differing properties of material withinthe refractory at varying heights.

In another aspect, the first plurality of bricks and the secondplurality of bricks may be staggered independently throughout therefractory, and may be staggered uniformly throughout the refractory,and may be staggered uniformly throughout the refractory forming ahoneycomb shape.

In a tenth broad aspect, the present invention provides a method ofmodifying an existing refractory in a metallurgical furnace for smeltingminerals, wherein the existing refractory surrounds a furnace space, fordissipating heat when the furnace space is heated. The method includesthe steps of providing an inner refractory layer within the existingrefractory, the inner refractory layer having a heat dissipationthickness, and the inner refractory layer including a first plurality ofbricks of a first type having the heat dissipation thickness, andincluding a second plurality of bricks of a second type having asacrificial thickness greater than the heat dissipation thickness, thesecond plurality of bricks protruding towards the furnace space.

In another aspect, the method includes step(s) of determining thesacrificial thickness from a predictable consistency of molten slagformed during use of the metallurgical furnace for smelting minerals,and/or determining the sacrificial thickness from a predictableconsistency of the molten metal during use of the metallurgical furnacefor smelting minerals.

In another aspect, the method includes the step of arranging the firstplurality of bricks and the second plurality of bricks in a staggeredmanner throughout the refractory, and/or a uniformly staggered mannerthroughout the refractory, and/or in a uniformly staggered mannerthroughout the refractory, thereby forming a honeycomb shape.

In an eleventh broad aspect, the present invention provides an electrodeseal for use in a metallurgical furnace. The furnace includes a furnacespace heated by electrodes extending through an aperture into thefurnace space, and the seal includes at least three sets of shoes inconsecutive lateral contact, each shoe having a biasing member, whichmay be a spring, which may further be replaceable, and which may also beadjustable to provide greater or less bias, for biasing a surface of theshoe towards one of the electrodes thereby allowing the one electrode tolongitudinally move within the electrode seal while providing electricalinsulation between the electrode and the aperture.

In another aspect, the at least three set of shoes provide a gap aroundthe electrode to allow for a free lateral movement of that electrode.

The biasing member may be adjustable to provide greater or less bias,with one end pressed upon the cooper shoe and the other end against anadjustable bronze screw. The biasing member may be electricallyinsulated on both ends, e.g., with plastic discs which are againstcopper shoe on one end and against the copper screw on the other.

The at least three sets of shoes may also comprise a first layer ofceramic inner shoes and a second layer of copper outer shoes, the twolayers of shoes forming a circle and an inner diameter of the circlebeing greater than the electrode thereby providing a gap therebetween.

The at least three sets of shoes may also be drilled through evenlydistributed holes from outside to inside.

In another aspect, the at least three sets of shoes allow for a lateralmovement of the one electrode therewithin while maintaining theelectrical insulation.

In another aspect, the seal may include electrical insulating materialpacked around an electrode above the at least three shoes, and theelectrical insulating material may be ceramic wool.

In another aspect, the seal may include using a chamber surrounding theshoes for containing pressurized electrically inert gas, for providing apressurized seal for preventing gas escape from the furnace space. Thepressurized gas may penetrate through the holes in the shoes and therebybe distributed around the electrode evenly to push down along theelectrode in order to contribute to preventing the furnace gas and dustsfrom within the furnace space flowing through the gap around theelectrode, in turn, thereby preventing at least some of the gas fromleaking and preventing at least some substance attached to the electrodefrom hindering vertical movement of the electrode.

In another aspect, the seal may include an electrically insulatedcooling member surrounding an electrode. The cooling member may includea cast copper plate, which may be protected from underneath by a durableinsulating material, which may be a castable material, for example ahigh alumina castable material.

In another aspect, the cast plate may define a contiguous inner channelfor directing cooling fluid flowing therethrough.

In another aspect, the cooling member may include a copper plate.

In another aspect, the chamber may be at least partly defined by thecooling member.

In a twelfth broad aspect, the present invention provides ametallurgical furnace including a refractory, surrounding a furnacespace, for dissipating heat when the furnace space is heated. Therefractory includes an inner layer having a heat dissipation thickness,the inner layer includes a first plurality of bricks of a first typehaving the heat dissipation thickness, and a second plurality of bricksof a second type having a sacrificial thickness greater than the heatdissipation thickness, the second plurality of bricks protruding towardsthe furnace space. The furnace also includes a force exerting member forcontracting a segmented outer shell around the refractory, toward thefurnace space, as the refractory contracts when the furnace space iscooling. The force exerting member includes a surrounding structure forsurrounding the segmented outer shell around the refractory, and atleast one tension member for exerting force on the surrounding structurefor contracting the segmented outer shell around the refractory, towardthe furnace space, as the refractory contracts when the furnace space iscooling. The furnace also includes a vertical compression member forexerting a compressive force upon the refractory, thereby verticallycompressing the refractory as the refractory contracts when the furnacespace is cooling. The furnace also includes a cooling system for coolingthe metallurgical furnace, the cooling system including an outer sleevesurrounding a layer of air heated by an inner furnace space of thefurnace, and one or more air displacement members for displacing theheated surrounding air away from the furnace. The furnace also includesa roof, including a roof member having suspension members extendingthrough an outer surface of the roof member, the suspension memberssupporting an inner mesh of the roof member, the inner mesh supportinginsulating material.

In thirteenth broad aspect, the present invention provides ametallurgical furnace comprising a refractory, surrounding a furnacespace, for dissipating heat when the furnace space is heated, therefractory comprising two pairs of planar and opposed walls, each memberof at least one pair of walls movable relative to the other member, eachwall comprising a segment of a segmented outer shell a plurality ofpressing members disposed around an outer surface of the segmented outershell, each pressing member for pressing against the outer surface andthereby exerting a compressive force thereon, thereby contracting thesegmented outer shell around the refractory, toward the furnace space,as the refractory contracts when the furnace space is cooling.

In another aspect, the pressing members allow the refractory to expandwhen the furnace space is heated and exert a compressive force on therefractory as the refractory contracts when the furnace space iscooling.

In another aspect, the pressing members comprise spring members.

In another aspect, the pressing members are adjustable to apply greateror lesser compressive force on the segmented outer shell.

In another aspect, the pressing members are biased against the outersurface of the segmented outer shell by biasing members.

In another aspect, the biasing members are adjustable to apply greateror lesser bias to the pressing members against the outer shell.

In another aspect, the biasing members are each threaded members forcooperation with a corresponding fixed member, whereby turning thebiasing member within the fixed member in results in displacement of thebiasing member relative to the outer shell, and results in applicationof greater or less bias to the pressing members against the outer shell.

In another aspect, the pressing members are supported on two or moresupport members.

In another aspect, the pressing members are supported on two or moresupport members which are vertical columns disposed around the segmentedouter shell.

In another aspect, the position of two or more of the vertical columnsis fixed.

In another aspect, the position of each of the vertical columns isfixed.

In another aspect, the vertical columns comprise first and secondvertical ends, and are fixed in position at at least one of the firstend and second vertical ends.

In another aspect, the vertical columns are buckstay columns.

In another aspect, the pressing members are biased against the outersurface of the segmented steel shell by biasing members, and wherein oneor more of the biasing members is supported by one or more of thevertical columns, or by horizontal beams fixed by two vertical columnsat both ends.

In another aspect, the refractory comprises an innermost layer ofthermally conductive bricks disposed around the furnace space forabsorbing and dissipating the heat.

In another aspect, the refractory further comprises at least oneadditional layer of thermally conductive bricks disposed around theinnermost layer of thermally conductive bricks, for further absorbingand dissipating the heat.

In another aspect, the additional layer comprises bricks comprising adifferent material than bricks of innermost layer.

In another aspect, at least some of the thermally conductive brickscomprise periclase.

In another aspect, the refractory further comprises an outer layer ofbricks disposed around the one or more layers of thermally conductivebricks.

In another aspect, the outer layer of bricks comprises a graphitematerial.

In another aspect, the refractory comprises at least one gap at a cornerbetween adjacent walls in an expanded configuration when the furnacespace is heated.

In another aspect, the furnace further comprises one or more sealingmembers for sealing the at least one gap at the corner between adjacentwalls in an expanded configuration when the furnace space is heated.

In another aspect, the one or more sealing members are strips forplacement between the outer layer of bricks and the one or more layersof thermally conductive bricks at a position for sealing the at leastone gap between adjacent walls in an expanded configuration when thefurnace space is heated.

In another aspect, the refractory, prior to the furnace space beinginitially heated, comprises at least one layer of spacer materialbetween the innermost and the least one additional layer of thermallyconductive bricks, thereby resulting in a refractory diameter largerthan a contracted configuration of the shell, and wherein the spacermaterial is made of a material adapted to combust or dissipate when thefurnace space is heated, thereby leaving space to compensate foradditional space occupied by expanding thermally conductive bricks.

In another aspect, the segmented outer shell comprises at least foursegments, each of the four segments corresponding with each of the fourwalls.

In another aspect, each segment of the segmented outer shell comprisesan edge which is adapted to cooperate with an edge of an adjacent shellsegment.

In another aspect, one or more segments of the segmented outer shellcomprise a flange mounted perpendicularly to a lower edge of thesegment, the flange for supporting the segment vertically.

In another aspect, the furnace comprises an outer layer of bricksdisposed around the one or more layers of thermally conductive bricks,and wherein the flange provides support for the outer layer of bricks.

In another aspect, the pressing members are biased against the outersurface of the segmented steel shell by biasing members, and one or ofthe biasing members is supported by one or more of the vertical columns,and further, the biasing members are threaded members for cooperationwith a corresponding fixed member, whereby turning a biasing memberwithin the fixed member in results in displacement of the biasing memberrelative to the outer shell, and results in application of greater orless bias to the pressing members against the outer shell, where thepressing members are biased against the outer surface of the segmentedsteel shell by the biasing members, and where each fixed member issupported by one or more of the vertical columns.

In a fourteenth broad aspect, the present invention provides a method ofadapting a metallurgical furnace comprising a refractory surrounding aninner furnace space, the refractory comprising a pair of opposed walls,the refractory for dissipating heat when the furnace space is heated,and comprising a contiguous rectangular-in-cross-section outer shellsurrounding the refractory, the method comprising dividing the outershell into a segmented outer shell comprising four planar segments anddisposing pressing members around the refractory, the pressing membersfor contracting the segmented outer shell, toward the furnace space, asthe refractory contracts when the furnace space is cooling.

In another aspect, the pressing members allow the refractory to expandwhen the furnace space is heated and exerts a compressive force on therefractory as the refractory contracts when the furnace space iscooling.

In another aspect, the pressing members comprise spring members biasedagainst the segmented outer shell.

In another aspect, the method further comprises replacing the refractorywith at least one inner layer of thermally conductive bricks surroundingthe inner furnace space, and with at least one outer layer of brickssurrounding the one or more inner layers.

In another aspect, the method further comprises disposing at least onelayer of spacer material between the thermally conductive bricks of thesame layer of refractory, thereby resulting in a diameter of therefractory larger than a contracted configuration of the shell, whereinthe spacer material comprises of a material adapted to combust ordissipate when the furnace space is heated, thereby leaving space tocompensate for additional space occupied by expanding thermallyconductive bricks.

In another aspect, the method further comprises providing a sealingmember at a corner between adjacent walls, each sealing member forsealing one or more gaps formed between the adjacent walls in anexpanded configuration when the furnace space is heated.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and exemplary advantages of the present invention willbecome apparent from the following detailed description, taken inconjunction with the appended drawings, in which:

FIG. 1 is a horizontal cross-sectional view depicting an exemplarymetallurgical furnace of the present invention.

FIG. 1A is a horizontal cross-section view partly depicting a lowerportion of an outer shell and related components of an exemplarymetallurgical furnace of the present invention.

FIG. 2 is a vertical cross-sectional view depicting an exemplarymetallurgical furnace of the present invention.

FIG. 2A is an elevational view partly depicting an inner surface of arefractory of an exemplary metallurgical furnace of the presentinvention.

FIG. 3 is a vertical cross-sectional view partly depicting an upperportion of a refractory and vertical compression members of an exemplarymetallurgical furnace of the present invention, and partly depicting anexemplary roof and an exemplary cooling system, both for metallurgicalfurnaces, of the present invention.

FIG. 3A is a detailed view of a single exemplary brick of an exemplaryrefractory for a metallurgical furnace of the present invention.

FIG. 4 is an elevational view partly depicting an exemplarymetallurgical furnace of the present invention and partly depicting anexemplary cooling system for a metallurgical furnace of the presentinvention.

FIG. 4A is a horizontal cross-sectional view depicting a refractory andvertical compression members of an exemplary metallurgical furnace ofthe present invention, and partly depicting an exemplary cooling systemincluding nozzles for spraying liquid coolant, all for a metallurgicalfurnace of the present invention.

FIG. 5 is a plan view depicting the top of an exemplary roof for ametallurgical furnace of the present invention.

FIG. 6 is a cross-sectional view depicting a portion of an exemplaryroof for a metallurgical furnace of the present invention.

FIG. 6A is a plan view depicting the bottom of a section of an exemplaryroof for a metallurgical furnace of the present invention.

FIG. 7 is a vertical cross-sectional view depicting an exemplaryelectrode seal for a metallurgical furnace of the present invention.

FIG. 8 is a horizontal cross-sectional view depicting an exemplaryelectrode seal for a metallurgical furnace of the present invention.

FIG. 9 is a horizontal cross-sectional view depicting an exemplaryelectrode seal for a metallurgical furnace of the present invention.

FIG. 10 is a side view depicting an exemplary electrode seal for ametallurgical furnace of the present invention.

FIG. 10A is a schematic top view depicting pressing member locations ofan exemplary metallurgical furnace of the present invention.

FIG. 10B is a schematic longitudinal view depicting pressing memberlocations of an exemplary metallurgical furnace of the presentinvention.

FIG. 10C is a schematic end view depicting pressing member locations ofan exemplary metallurgical furnace of the present invention.

FIG. 11 is a top view of an arrangement of an exemplary metallurgicalfurnace according to the present invention.

DETAILED DESCRIPTION

Different embodiments address different aspects of the furnace design.It will be understood that not all of the different aspects of thefurnace design discussed herein are required for at least some drawbacksknown in existing designs to be addressed. In some cases, single aspectsdescribed herein may independently address at least certain knowndrawbacks. While there exist synergies between the various exemplaryembodiments, the embodiments are expected to work with otherconventional furnace designs (e.g., conventional brick refractory and/orelectrode and/or external cooling system and/or roof designs).

A brick refractory may be made of multiple lateral, or radial, layers ofbricks, placed adjacent to one another. Individual layers may be made tointerlock, which may provide additional stability. During use, theheating of the brick refractory causes thermal expansion of the bricks.In order to compensate for this expansion, there may be expansion papersplaced between the individual horizontal, and/or vertical, layers ofbricks prior to first use of the furnace therewith. Once heated, thesepapers burn, providing space for the layers of brick to expand in bothhorizontal and vertical axes. Between the outermost layer of bricks andan outer steel shell, some furnaces may have a layer of expansion board.This layer is elastic in nature, and is intended to allow the outermostlayer of bricks to expand without pressing upon the inside surface ofthe steel shell, thus minimizing stress to the brick refractory.

When exposed to numerous cycles of furnace heating and cooling, thebricks may present flaws. For example, when the expansion papers haveburned away, they cannot be easily replaced prior to further heatingcycles. Thus, further cycles of heating and cooling will typicallyresult in gaps between the bricks, increasing heat escape from thefurnace if the ambient air flows around it, as may also result in escapeof molten metal from the furnace, into the brickwork of the brickrefractory. Additionally, the cycles of expansion and contraction mayresult in friction and pressure between the bricks, and eventuallywearing down and breakdown of the bricks, which may ultimately result infailure of the brick refractory. Additionally, the expansion boardstypically used to fill the space between the outer steel shell and thebrick refractory have a limited lifespan, and lose their elasticity witheach cycle, resulting in space between the brick refractory and theshell. The gaps between the bricks may further result in instability ofthe brick refractory, which eventually may contribute to the wearing andbreakdown of the bricks. The gaps between the bricks are also known todecrease cooling efficiency of some furnaces.

In some examples, each layer of bricks may be staggered and interlockedwith respect to the layer immediately above or below. The bricks arebound and held together by the structure defined by an outer steelshell, with all bricks being effectively interlocked together, resultingin an initially strong structure. However, after a series of thermalcycling, the bricks may begin to crack and wear down. For example, sincebricks closer to the heated furnace space may become hotter, they mayalso be subject to greater thermal expansion, as compared with thosefarther away from the heated furnace space. As these bricks expandvertically, the interlocking manner in which they are laid may result instress on the expanding bricks. This effect may be more pronounced incases where furnaces are shut down for longer times and then reheatedrapidly.

Brick integrity may be vulnerable when the frozen “skull” layer of slaginside the furnace cracks and forms gaps during cooling, partly as aresult of differing densities of different molten materials and solids.In cases where the skull has cracked during cooling and the furnace israpidly reheated, the likelihood of a furnace “runout”, where moltenmaterials leak through the skull and then through spaces in the brickrefractory and eventually out of the furnace, is increased.

Above the freeboard, metallurgical furnaces typically have some form ofroof. The roof may be partly supported by the furnace itself. The roofmay also be supported, in whole or in part, by external supporting means(for example, the structure or building in which the furnace is housed).In use, fumes and dust may deposit on the lower surface of the roof, andthese deposits may have a thickness of 10 to 20 cm. The temperature onthis lower surface of the roof may reach approximately 1200 to 1600degrees Celsius during use.

The roof may be made of castable material, which is not conductive toelectricity or heat. In some examples, the roof may have a maximumthickness of 10 to 20 cm of high alumina castables, which are suspendedby a steel anchor fixed to a water cooled steel panel. The roof aims atto provide thermal insulation for the surrounding environment and/or toprovide a barrier to prevent the escape of toxic gases, including carbonmonoxide, into the surrounding environment, which contributes tocreating a safe environment for workers.

Electrical furnaces typically have one or more electrodes suspended fromabove the furnace. The high temperature created by the electrodes mayheat the surrounding roof area. Additionally, the high voltage runningthrough the electrodes may cause a risk of electrocution for workersworking near the furnace roof.

A cooling system may be provided for the furnace using water sprayed, orfalling as a film, on an external surface of the furnace. Excess water,however, may pose a safety risk, especially in situations where moltenmetal escapes from the furnace, e.g., due to an integrity failure in thefurnace (commonly referred to as a “run-out”).

Reference is now made to the drawings, in which FIG. 1 shows ahorizontal cross-section or top view of an exemplary metallurgicalfurnace 10 in accordance with one embodiment of the present invention.The furnace 10 depicted is round in shape along the horizontalcross-section shown. The section shown is from the “freeboard” space ofthe furnace. The freeboard space is above the “slag line” in the furnace10, above which there is typically no molten or solid metal or slag inthe furnace during operation. A brick refractory 20 of the furnace 10 atthis space may be in direct contact with either fume or dust materialfrom the furnace 10, or in direct contact with heated furnace gas. FIG.1A shows a horizontal cross-section view partly depicting a lowerportion of an outer shell 40 and related components of the exemplarymetallurgical furnace depicted in FIG. 1. The furnace 10 is surroundedby an exterior sleeve 520 discussed further below, and is supported by anumber of structural columns 70, which may be steel buckstay columns.

Reference is now made concurrently to FIGS. 1 to 4A. With reference toFIG. 2, the furnace 10 depicted comprises the brick refractory 20radially surrounding an inner furnace space 30 and the outer shell 40radially surrounding the brick refractory 20. Below the inner furnacespace 30, a brickwork hearth 45 may comprise four layers of brick, whichmay be periclase bricks (e.g., inner layer(s)) and graphite bricks(e.g., outer layer(s)). Expansion papers or graphite felt layers (notshown) may be placed between these bricks. A steel structure as asegment of a sphere, part of the outer shell 40 and depicted at thebottom, supports the brickwork hearth 45 which contain molten metal orslag, or other materials that are heated or are to be heated in thefurnace 10.

The furnace 10 depicted in the example of FIG. 2 comprises exteriorsleeve 520 discussed further below, and is supported by a number ofstructural columns 70, and is covered by a roof 200, in which there areopenings through which electrodes 400 are shown protruding. Theexemplary roof 200 will be described more specifically with reference toFIGS. 6 and 6A. In the example of FIG. 2, the electrodes 400 areradially surrounded by non-conductive shoes 415 and 410, which will bedescribed more specifically with reference to FIGS. 7 to 9. Still withreference to FIG. 2, air displacement members 500 are depicted for usein moving heated air away from an envelope of air surrounding thefurnace 10. With reference to FIG. 4 and FIG. 4A, ambient or cooled airis allowed to enter the envelope of air through air ingress apertures510 in the exterior sleeve 520 to replace the heated air which has beendisplaced away. Liquid coolant spraying means or mechanism 540 may beused to spray a fine mist of liquid coolant, for example water, onto theexterior steel shell 40 of the furnace 10, thereby cooling the furnace10, in accordance with certain preferred embodiments of the presentinvention. In the example of FIG. 4A, the liquid coolant spraying means540 is organized as an array of water spray nozzles 545. Otherconfigurations could be used without affecting the end result sought(e.g., one or more mister positioned along columns 70). The liquidcoolant spraying means 540 may be configured to spray water at a fixedvolume or at a variable volume. The liquid coolant spraying means 540may be configured to monitor the temperature of the exterior sleeve 520and adjust the volume and/or spray time considering the temperature. Theliquid coolant spraying means 540 may further comprise a water detector(not shown) that transmits an alarm and/or shuts the system off whenwater is detected to be accumulating. The liquid coolant spraying means540 may further comprise a thermometer and a hygrometer (not shown) thatmonitor the temperature and humidity of the air at one or more specificlocations (not shown) around the exterior sleeve 520 and adjusts thevolume and/or spray time in accordance therewith. In preferredembodiments, the surface of the shell 40 and the surrounding air asmeasured from within the sleeve 520 may not exceed temperatures of 80 Cduring use, and the air temperature may be lower than that of thesurface of the shell 40, while maximum air humidity may be at or around100% at 80 C.

In the example of FIGS. 1, 2 and 4, the brick refractory 20 is comprisedof an inner layer of brick 22 radially surrounding the inner furnacespace 30, a second layer of brick 24 radially surrounding the innerlayer 22, and an outer layer of brick 26, radially surrounding thesecond layer 24. In other embodiments, one, two, three, or more layersof brick may be used. The number of layers may vary depending on themolten materials inside the furnace 10 during use. The layers of bricksmay be of varying thickness, e.g., radially increasing thickness, whichmay be particularly suited for use cases where greater pressures areexpected to be exerted on the brick refractory 20 during use, or foruses where the contained materials have a relatively low thermalconductivity for solidified skull.

In preferred embodiments, in order to facilitate locking of a slag“skull” onto the brick refractory 20, the hot (i.e., inner) face of theinnermost layer 24 of periclase brick 22 may be formed with differentthickness of bricks. In further preferred embodiments, bricks ofdiffering thicknesses may be arranged in a staggered form, to provide ahoneycomb-like shaped refractory interior as depicted in FIGS. 2, 2A and4A. In some embodiments, only the inner face of the bricks in the slagarea are in such arrangement.

In use, for example at start-up of a metallurgical furnace having a newrefractory of the type of the refractory 20, a refractory wherein theinnermost layer 22 comprises bricks of differing thicknesses, forexample in a honeycomb-like formation as depicted in FIG. 2A, may allowhot slag and/or molten metal, as well as dust and other materials at thefreeboard space, to adhere or freeze, as appropriate, to theinner-facing surface of the refractory. The innermost surface of thebricks having the greatest thickness 2200 may, during use, be corrodedor broken down by chemical or mechanical action, although the overallintegrity and strength of the refractory is not compromised.Accordingly, these innermost portions of these thickest bricks 2200 maybe considered to be “sacrificial”. In order to reduce possibly corrosionof the surface of these bricks, initially a layer of castables which maybe approximately 50 mm thick, and which may be made of magnesium oxides,may be casted on top of all the interior surface of refractory which mayform a staggered or in “honeycomb” shape.

In preferred embodiments, the inner 22 and second 24 layers of bricksmay comprise bricks made of a thermally conductive material, forabsorbing and dissipating heat from molten metal and slag, and fromheated furnace gas, all inside of the furnace. Other materials such aschrome based refractory are suitable for nonferrous ore smelting.Mag-graphite refractory is also suitable for ferrous ore smelting.Silica and alumina based refractory may also be suitable depending onthe properties of the contained materials. In further preferredembodiments, these layers may comprise a magnesium oxide, or periclase,material for titaniferrous ore (e.g. ilmenite) smelting. The outer layer26 of brick may comprise a graphite material. One or more outer layers26 having high thermal conductivity may provide an advantageous benefit,e.g., in cases where molten materials leak through the inner refractorylayers 22 and 24. As the outer layer 26 may be at a similar temperatureto that of the steel shell 40, it may advantageously cause the leakedmaterials to cool and solidify rapidly, preventing a runout. In suchcases, the outer layer 26 may function as an extension of the steelshell 40 thermally, but with a much higher resistance to the hot moltenmaterials.

In preferred embodiments, the outer layer 26 of bricks will comprisegraphite-containing bricks. The graphite brick thickness may varybetween 150 to 300 mm, depending on the furnace 10 power level. Forexample, the graphite bricks may have a size of 150 mm×230 mm×100 mm.The physical size of a brick to be used may vary depending on its weightfor ease of transport and use. As an example, a first layer of thegraphite bricks is laid from the bottom to the top with the 100 mm sidevertically, 150 mm side laterally and 230 mm side radially. These bricksmay be staggered in the vertical direction, and laid directly upon oneanother vertically without any expansion paper or cement of any kind.

FIG. 3A shows an exemplary brick 4000 of the exemplary refractory 20 inaccordance with one exemplary embodiment. In order to compensate fordifferences in vertical expansion within a single radial layer of brick,in some embodiments, the brick 4000 may be configured appropriately, asexemplified on FIG. 3A. On FIG. 3A, three axes (x, y, z) arerepresented. For the purpose of the example, a heat source is expectedon the surface 4020 or plane y′-z′. Heat would thus be higher, in use,on the concave face (interior) 4020 of the brick 4000 than on the convexface or plane y-z. The height of the brick 4000 along the y axis on theinterior face 4020 (y′) could be less than at the exterior face (y) inorder to compensate for varying expansion between the two faces. For theexample of FIG. 3A, the lateral profile 4080 of the brick 4000 is aisosceles trapezoid, with the x being equal to x′. Skilled person willunderstand that the profile could also be a rectangular trapezoid oranother type of trapezoid (where x and x′ would be different) as long asthe desired difference between y and y′ is established. In the presentexample, because the difference for each brick is so small a reasonablecorrection may only be required for 4-5 bricks combined. Similarly, thelength of the brick 4000 on the interior face 4020 (y′-z′) could besmaller than the expected arc length at the exterior face (y-z). To alesser extent, the length on the interior face 4020 at the bottom of thebrick 400 (z″) could be less than at the top of the same face (z′) if avertical temperature gradient exists.

A skilled person will readily understand that the configuration of thebrick 4000 will have to take into account the stackability thereof. Itmay prove difficult to have adjusted dimensions on the height and lengthwhile making sure that the layers 22, 24 and/or 26 can be assembled fromthe brick 4000. In certain embodiments, only one of the dimension may beselected for adjustment. Another solution is to maintain a flat backportion of the brick 4040, which ensures stable stackablity, while afront portion 4060 is shaped considering varying expansion based on heatdissipation, as exemplified above. Yet another solution is to have adistribution of the configured bricks in the layer 22, 24 and/or 26 soas to provide stability. For instance, the varying configuration couldbe applied throughout a layer of bricks, but could also vary dependingon the position of the brick 4000 in the stack. The varyingconfiguration could also be applied to only some of the stacked bricksand not to others, e.g., on bricks surrounded by normal bricks, ondiagonal series of bricks, etc.

For example, for an inner layer of brick having a cool vertical heightof 4″ or 101.6 mm per brick 4000, experiencing temperatures of 800degrees Celsius on the inner face 4020, and 400 degrees Celsius on theouter face, with the inner layer having a height of 11 m, a correctionmay be made to the shape of the bricks, of approximately 3 mm (i.e. thebrick is 3 mm taller at its outer face than inner face), for everyfourth vertical layer of bricks, except for the top eight layers ofbricks. Skilled persons will readily appreciate the appropriate degreeof correction to be made to compensate for uneven vertical thermalexpansion experienced by a single radial layer of brick.

The inner 22 and second 24 layers of bricks may be laid in the samefashion as the outer 26 layer. In these embodiments, the three layers22, 24, 26 of bricks are thus independent of one another vertically.

In preferred embodiments, the bricks of each layer of the refractory 20are configured to form a series of circular layers, stacked on top ofone another, by having two side ends cut at an appropriate angle and afront and back end cut an appropriate shape, such that when a sufficientnumber of the bricks is positioned adjacent to one another, side end toside end, a circle is formed, which circle is thus resistant to anyhorizontal compressive force.

In the furnaces 10 depicted in FIGS. 1 and 2, the refractory 20 ishoused in the shell 40, which may be cylindrical in shape, and may bemade of steel. Skilled persons will recognize that other metals ormaterials may also be suitable for the shell 40 material. In thedepicted example, the shell 40 is divided into several sections 42divided by vertical cuts 44 or gaps between adjacent sections 42. In theembodiment depicted in FIG. 1, the shell 40 is divided into eightsections 42. In general, increasing the number of shell sections 42 willincrease the uniformity of distribution of stress imparted on therefractory 20 during expansion and contraction, and larger numbers ofshell segments 42 may be appropriate in cases where the overall furnacesize is relatively larger, where as smaller numbers may be appropriatefor relatively smaller furnaces. In preferred embodiments, in eachsection a plate of ring steel or the same material as the shell iswelded at the bottom ends of the shell plate, functioning as a flange46. Holes may be made to allow bolting the shell plate on the bottomflange in the hearth 47 depicted in FIG. 4A. A clearance of 60-70 mm gapbetween each shell section 42 may be required for the present example.In the example depicted in FIG. 1A on each side of shell plate 42 astrip is welded on as a flange 43. Holes on the flange are made to allowlong screws 41 bolted onto the same flange of adjacent plate. The screwsare positioned so that the clearance of 60-70 mm gap can exist. A numberof screws 41 may be adjusted accordingly to withstand the ferrostaticpressure from within the furnace 10 during operation to lock a maximumexpanded position of the shell 42. In order to avoid furnace gas leakingthrough this gap, thin strips, which may comprise steel or any othersuitable material, may be placed behind the outer brick layer 26 againstthe shell sections 42 to cover the gap. The width of the strips may beslightly larger than the gap to form a seal between the two adjacentshell sections 42. In other embodiments, flanges 43 may comprise anexpandable material configured to provide a seal between two adjacentshell sections. Skilled persons will readily appreciate that othersuitable sealing means may be used to provide a gas seal betweenadjacent shell sections 42, thereby preventing gas escape or ingressduring expansion and contraction of the refractory 20 and correspondingmovement of adjacent shell sections 42 away from one another. Inpreferred embodiments, after all the sections of shell plate are fixedand installed, bricks 26, 24, and 22 may be laid against the shellplate. When the furnace 10 is ready to start up, the bolts at the bottomflange 46 may be removed and the shell plates may then move freely asthey expand or contract. Displaced horizontally about the shell sections42 are one or more force exerting members comprising binding members 50and tension members 60. Compression members (not shown) may possibly beused, but they would likely fail to provide a range of self-adjustmentthat is large enough for many situations.

In preferred embodiments, the binding members 50 may be steel cables,which may be braided steel cables comprising numerous steel filaments orwires, although skilled persons will readily appreciate that many otherforms of binding members 50 may be suitable. The binding members 50 areunder a tension, such that a compressive force is applied to the shellsections 42, which transfers this compressive force to the refractory20. Each of the shell segments 42 may be made of individual plateswelded together. Welds may be subject to fatigue, especially ifconstantly under a bending moment. Having the outer shell 40 segmentedtogether with the force exerting members, when used properly, maydiminish the bending moment that welds may sustain.

To reduce the likelihood that the binding force at normal operatingcondition will exceed the maximum tension capacity, the retainingmembers 41, which may be screws, may fix the position of the shellplates 42. When the shell sections 42 expand to a locking position, theywill be impaired from further expansion, and the ferrostatic pressurefrom within may be withheld by the locked shell sections 42, rather thanby the tension members or binding members.

In preferred embodiments, the binding members 50 are maintained undertension by the use of tension members 60 loaded onto the binding members50. In certain preferred embodiments, the tension members 60 are heavyduty springs.

In some embodiments, the force exerting member comprises a plurality ofpressing members disposed around an outer surface of the segmented outershell 40, each pressing member for pressing against the outer surfaceand thereby exerting a compressive force thereon. These pressing membersmay be springs, configured to press directly on the outer surface of thesteel shell segments, or may be shoes, configured to press against theouter surface, and may be biased against the steel surface, for exampleby springs (not shown). In some embodiments, the pressing members may beadjustable to apply greater or lesser compressive force on the segmentedouter shell 40. In some embodiments, the pressing members may besupported by a support structure, which may be external to themetallurgical furnace 10, for example steel buckstay columns 70surrounding the metallurgical furnace 10 and connected to one anotherlaterally. Skilled persons will readily appreciate the appropriatenumber, form, and configuration of support structures for supporting thepressing members considering, e.g., dimensions of the furnace 10 andexpected forces.

In the embodiments depicted in FIGS. 1 and 2, the binding members 50 aresupported by a plurality of vertical columns 70. In the depictedembodiments, the vertical columns 70 are four buckstay columns,distributed radially and evenly, at 90 degree angles from one another,around the shell 40. Skilled persons will readily understand that moreor less support columns 70 could be used without affecting the teachingsof the present invention. In applications where the capacity of thetension members 60 available is not large enough, more binding members50 and tension members 60 may be required, and the number of columns 70and tension members 60 may vary in order to accommodate the need oftotal binding force, particularly for the metal area at the lower partof the furnace 10. With reference to FIG. 4, in preferred embodiments ofthe present invention, four pairs of steel cables functioning as bindingmembers 50 are positioned along the height of the furnace 10, with eachpair positioned such that each member of a pair of tension members 60corresponding with a pair of binding members 50 are positioned radiallyopposite one another. The use of multiple pairs of cables, whileoptional, aims at reducing the possibility of failure of the bindingsystem. Similarly, it is unlikely that both cables in a pair would failsimultaneously. Additionally, the use of multiple cables, once thebinding system is dimensioned appropriately, provides the exemplaryadvantage of facilitating maintenance of the binding system, as onemember fails, others may be of sufficient strength to functionindependently. Thus, if a tension member 60 or a binding member 50requires replacement or repair, that tension member 60 or binding member50 may be removed without removal of the other member of the pair, andtherefore without having an impact on the function of the horizontalbinding system overall. Furthermore, with the aforementioned lockingsystem, the maintenance of the binding members 50 and tension members 60may be further facilitated.

With reference to FIGS. 1 and 2, in preferred embodiments, the bindingmembers are exemplified as steel cables 50 supported and maintained inplace by positioning members 52 which may be wheel members mounted ontothe buckstay vertical columns 70. These positioning members 52 allow forexpected movement of the steel cables 50 relative to the shell sections42, and vice versa.

In certain preferred embodiments, a mechanism or means to measure thetension goes along with the tension members 60. That may facilitatemonitoring and maintaining a target tension in the binding members 50.These means are, in preferred embodiments, a scale to measure theelongation of the springs as the tension equals to the elongationmultiplied by the spring constant of the tension members 60. Tension maybe adjusted through use of a length adjustment device 90, which isexemplified as a turnbuckle, for adjusting the length, and therefore thetension, of the binding members 50. As a result of the binding members50 being under tension, a compressive force will be applied to the shell40, and thus on the refractory 20. Higher tension will result in agreater compressive force being placed on the refractory 20. Inpreferred embodiments, the compressive force, and therefore the tension,suitable to maintain radial stability of the refractory 20 around thefreeboard space will be relatively lower when compared to that suitableto maintain stability of the refractory 20 around the lower portion ofthe furnace 10 containing molten materials or materials to be heated. Asthe ferrostatic pressure increases at lower part of the furnacecontaining molten metal, if the binding force does not increase inaccordance with the pressure, the lower part of the shell sections 42may bulge and cause tilting of the whole section. A level device maythus be placed on the bottom flange to determine whether it is at ornear level. Tension may be increased at lower part by shortening thelength of binding member 50 to tighten the shell sections 42 to keep theflange in a generally horizontal position.

During use, the refractory 20 is heated, and may have a thermal gradientranging from approximately 1000 degrees Celsius at its inner surfacedecreasing to approximately 80 degrees Celsius at its outer surface.When heated, the refractory 20 may expand in all directions. Inpreferred embodiments, the inner 22 and second 24 layers of periclasebricks will absorb and diffuse heat, and will expand to an expanded sizewhich will vary depending on the temperature to which the individualbrick is heated. For example, bricks closer to or in direct contact withmolten metal or slag, or in direct contact with heated furnace gasinside the furnace space, will be hotter, and therefore more expanded,than bricks which are not in direct contact with molten metal or slag,or heated furnace gas. It should be noted that in use, some of thebricks of the lower portion of the inner layer 22 will likely be coatedin a “frozen” or solid “skull” of slag or metal, which may have amelting point ranging from 1000 to 1600 degrees Celsius. By maintainingthe brick refractory 20 at a target temperature range, this skull willremain solid and may act as a lining to the furnace 10, which mayprovide additional stability to the furnace 10, and which may functionto limit escape of molten metal or slag into the brickwork of therefractory 20. As an example of a typical ilmenite smelting furnace, theslag contains over 80% TiO2 with a liquidus temperature of 1640 C, themolten slag freezes as it contacts the refractory 20 at 800 to 1000 C.The frozen slag as “skull” prevents further attack of molten slag on therefractory 20. By experience, it was not possible to identify a knownoxide material that could resist the corrosion of molten high TiO2 slag,except for refractory metals such as molybdenum, tantalum, and,platinum. A key aspect of smelting ilmenite ore is to control thisfrozen slag skull and maintain it at around 300 mm thick as a safetarget.

In preferred embodiments of the present invention, the refractory 20 isinitially assembled with expansion papers (not shown), which may have athickness of approximately 0.4 mm, placed between radial layers ofbricks. The thickness of the papers used is calculated so as tocompensate for the expected expansion of the bricks, and the overalldiameter of the furnace 10, including the papers, is therefore intendedto approximate the expected expanded configuration of the furnace 10.Once heated during use, the expansion papers will burn, leaving spacefor the refractory 20 bricks to expand and fill the spaces. In preferredembodiments, where an outer layer of bricks 26 comprises graphite,graphite felt may be used in place of expansion papers at the outerlayer.

During the first use, as the refractory 20, brick members expandlaterally (which form of expansion may also be referred to as“horizontally” or “radially” herein), the overall diameter of therefractory 20 should remain that of a generally constant expanded, orheated, configuration, in view of the burning of the expansion papers asdiscussed above. However, when the furnace 10 is cooled, the refractory20 will cool and contract, and the refractory 20 will contract to acontracted configuration, having a reduced diameter.

In preferred embodiments, the steel shell 40 will have a first diameterthat corresponds with a contracted configuration of the refractory 20.The steel shell 40 may be manufactured as a generally cylindrical shell,having the first diameter, and then cut with a series of vertical cuts44 to form a set of at least three, or at least eight, shell sections42.

When the refractory 20 is assembled, including expansion papers, asnoted above, the refractory 20 may have a diameter corresponding with anexpanded configuration. As discussed above, the steel shell 40, maycomprise a set of curved shell sections 42, which collectively form acylinder having a diameter corresponding with a contracted configurationof the refractory 20. Accordingly, when the steel shell sections 42 areassembled around the assembled refractory 20, there may be gaps orspaces formed between adjacent shell sections 42.

When the furnace 10 is cooled, for example during a period ofmaintenance or non-use, the bricks forming the refractory 20 will cooland contract. At the same time, the compressive force applied to thesteel shell 40 will force the shell sections 42 generally toward avertical axis at the centre of the furnace 10, and the gaps or spacesbetween adjacent segments 42 will lessen or disappear when the entirefurnace is cooled to room temperature. In preferred embodiments, thecompressive force will similarly force the contracting bricks inwardtoward the centre of the furnace 10, thereby reducing formations of gapsor spaces between the bricks. The tension of the binding members 50 willreduce or relax as the refractory 20 enters a contracted configuration,the length adjustment device 90, which may be a turnbuckle, may be usedto reduce the length of binding members 50 while maintaining the samebinding force when beyond the automatic adjustment range, therebypermitting the refractory 20 bricks, when eventually reheated, to expandagainst one another with the adjustment of the length of the bindingmembers 50 when the expansion is beyond the automatic adjustment range.

When the furnace 10 is heated again, the refractory 20 will heat up andexpand to an expanded configuration, having a relatively increaseddiameter. As the refractory 20 expands, spaces or gaps will occurbetween adjacent segments 42 of the shell 40, and the binding members 50(e.g., steel cable) will move as the tension member 60 (e.g., springs)stretch and expand to compensate for the expansion of the shell 40.During this expansion, movement of the cables relative to the shellsegments 42 may cause rolling of the positioning members 52, which mayturn to allow the movement while reducing friction and wear on thebinding members 50 which may be lengthened through turnbuckle 90.

In preferred embodiments, the refractory 20 and the shell 40 compressesbrick layers 48 and 49 of the hearth refractory 45. In theseembodiments, expansion papers may be placed between layers 48 and 49during furnace installation, in order to provide space between thelayers 48 and 49 prior to furnace use.

The process of furnace heating and cooling, and resulting expansion andcontraction of the refractory 20, may be repeated through multiplecycles, with the binding members 50 maintained under tension andapplying a compressive force, thereby reducing formation of gaps betweenbricks between cycles and increasing the stability of the bricks in therefractory 20 during the heating and cooling cycles. Furthermore, aspace between bricks may be provided, for example with expansion papers,to reduce thermal stress generated during the initial furnace expansionat startup.

With particular reference to the example of FIGS. 2 and 3, preferredmetallurgical furnaces 10 in accordance with some exemplary embodimentsof the present invention comprise a mechanism for compensation ofvertical expansion and contraction of the refractory 20, for exampleduring heating and cooling.

As shown in FIG. 3, in preferred embodiments, covering members 104, eachhaving a different diameter corresponding with the diameter of one ofthe layers 22, 24, 26 of refractory brick, are disposed above therefractory 20. Furnaces built in accordance with the present inventionmay be square, rectangular, hexagonal, octagonal or otherwise presentsome straight segments in horizontal cross section. In these examples,the covering members 104 would be shaped appropriately (square,rectangular, or otherwise), whereas in furnaces that are round inhorizontal cross section, the covering members 104 may be round inshape. In preferred embodiments, each of the covering members 104 hasouter and inner diameters approximately the same as an outer diameter ofthe corresponding brick layer, although other embodiments, for examplewhere the outer diameter of the covering member 104 is less than that ofthe corresponding brick layer, and/or the inner diameter is also lessthan that of the corresponding brick layer, may be used. In preferredembodiments, the covering member 104 comprises a single contiguous piecehaving a circumference, but skilled persons will readily appreciate thatcovering members 104 may also comprise a plurality of separate segmentsor broken rings. Between covering members 104 and the refractory 20, athin layer of elastic material such as Teflon™ (not shown) may be placedas a seal, which may prevent any leak of gas through the refractory.Similar material may also be placed between refractory 22 and 24, andrefractory 24 and 26, at the top bricks to improve sealing.

In preferred embodiments, a plurality of pressure members 100 isdisposed around the circumference of each covering member 104. Infurther embodiments, no covering members 104 are required, and thepressure members 100 are directly in contact with an upper surface of arefractory layer. In other embodiments, the covering member 104 maycomprise a plurality of segments, or individual plates may be placedover individual bricks or sequences of bricks. In still furtherembodiments, a single covering member or other member may be disposedover more than one radial layer of bricks.

The pressure members 100 are adapted to exert downward pressure or forceupon the refractory 20. In use, when the refractory 20 is heated, theresulting thermal expansion of the bricks will result in expansion ofthe refractory 20 to an expanded configuration. As discussed above, thisexpansion will be in all directions, including vertical. Thus, theoverall height of each of the layers 22, 24, 26 of brick in therefractory 20 will vary as the bricks are heated and cooled with thermalcycling of the furnace 10. Also as discussed above, the inner layer 22will be exposed to higher temperatures, and therefore greater thermalexpansion, than will the second 24 layer, and so on. Accordingly, theheight of the inner 22 layer in an expanded configuration, unlesspreconfigured otherwise, is expected to be somewhat greater than that ofthe second 24 layer or outer 26 layer.

In preferred embodiments, the pressure members 100 are steel springs,housed in a cap 102 disposed upon a surface of each covering member 104.In further preferred embodiments, the pressure members 100 are radiallyand evenly distributed around the circumference of each covering member104.

In the embodiment depicted in FIG. 3, the pressure members 100 aremounted to a pressure adjusting member 110, which is in turn mounted toa suspension member 120 which may be rigid. In preferred embodiments,the pressure adjusting member 110 may be a length adjustment device, andthe rigid suspension member 120 may be a steel rod. In further preferredembodiments, the pressure adjusting member 110 and the rigid suspensionmember 120 may be manufactured from a single steel rod which is cut andconnected by a threaded connection to allow for adjustment of thecombined length of the rigid suspension member 120 and the pressureadjusting member 110. By adjusting the combined length the rigidsuspension member 120 and the pressure adjusting member 110, thedownward force exerted upon the refractory 20 is also adjusted, and maytherefore be maintained at a target level.

In use, as the refractory 20 is heated and cooled, and expands andcontracts vertically, the pressure members 100 contract and expand incompensation, always forcing the refractory 20 downward, which aims atincreasing vertical stability of the refractory 20. In this way, it isexpected that formation of spaces and unevenness of the vertical layersmay be minimized. In particular, in one example, where each verticallayer of refractory bricks is independent from one another, without anycement or other binding material between vertical layers, the increasedvertical stability provided by this system may improve the overallstability of the structure and may increase the lifespan of the furnace10.

In the embodiment depicted in FIG. 3, the rigid suspension members 120are movably mounted to a horizontal supporting member or beam 130 byhorizontal sliding members or rolling members 140. During use, as therefractory 20 expands or contracts radially or horizontally, the rigidsuspension members 120 may also move a corresponding distance. In doingso, the direction of the force exerted by the pressure member 100 may bealigned with the center of gravity of each layer of the refractory 20.This may limit or eliminate the possibility of sliding of refractorywhich may otherwise result in a collapse. In preferred embodiments, thering members 104, if included, will be divided into a number of segmentsto allow the overall expansion and contraction of the refractory 20.

In certain embodiments of the present invention, existing radiallysymmetric or “circular” metallurgical furnaces may be adapted or“retrofitted”. In preferred methods, the outer cylindrical steel shellof an existing furnace is cut into a number of, for example, three,eight, or more than eight, shell segments.

In preferred methods, one or more binding members are disposedhorizontally about the cut steel shell. These binding members are placedunder tension, which may be maintained by loading tension members, whichmay be heavy duty springs, onto the binding members. In preferredembodiments, the binding members are steel cables, and are arranged inone or more pairs distributed along the height of the cut shell. Thebinding members under tension exert a compressive, or inward, force on arefractory within the cut shell of the retrofitted furnace.

When heated and cooled, the refractory of the retrofitted furnace willexpand and contract, and the steel shell segments will move inwardly andoutwardly in response to expansion and contraction of the refractory,held in place by the binding members, as the tension members expand andcontract. The tension may be maintained, adjusted and/or monitored byloading length adjustment members and tension measuring members onto thebinding members.

Preferred methods of retrofitting or adapting existing furnaces alsoinclude a step of replacing the refractory. Once replaced, therefractory may comprise an inner layer of bricks, which may each beradially symmetric in horizontal cross section, with an inner and secondlayer comprising thermally dispersive material such as periclase, andthe outer layer, next to the shell comprising a material which may havea high thermal conductivity, for example graphite. In preferredembodiments, the layers of bricks will be staggered vertically, andvertical layers will be independent from one another.

In preferred methods, a flange may be attached, for example welded, onthe end(s) of (a) curved shell segment(s) before furnace start-up. Shellsections may be bolted on the flange to fix with a hearth flangepositioned at the bottom. Once the bricks are assembled, the bolts areremoved from the retrofitted furnace to allow for movement of thesegments relative to the refractory.

In preferred embodiments, expansion papers may be placed between theradial layers of bricks to approximate a refractory diametercorresponding with an expanded configuration. Once heated during furnaceuse, these papers will burn, and the expanding bricks will fill theresulting spaces.

In still further preferred embodiments, methods of retrofitting oradapting existing radially symmetric furnaces, or furnaces that aresquare or rectangular in horizontal cross-section, include steps toinstall a vertical binding system for increasing vertical stability ofthe refractory. Installing the vertical binding system may includedisposing one or more pressure members above the refractory for exertingdownward pressure on the refractory. Preferred methods may includedisposing the pressure members on covering members or other membersabove a radial layer of refractory brick. Where covering members areused, one covering member for each of the two, three, or more radiallayers of brick may be used. The pressure members may be mounted orwelded on a surface of the covering members or other members, and may behoused in a cap. Rigid suspension members, which may be steel rods, maybe mounted to the pressure members, which may be springs. In preferredembodiments, the rigid suspension members will then be movably orslidably connected to horizontal support members, which may be steelbeams. By the movable connection, the rigid suspension members arepermitted to move back and forth horizontally in compensation for radialexpansion and contraction of the refractory from an expanded position(heated) to a contracted position (cooled).

With reference to FIG. 5, preferred embodiments of the present inventioncomprise a roof 200. In use, the lower surface of the roof 200, facingtoward the inner furnace space 30, as shown in FIG. 1, may be coatedwith a layer of dusts and other materials generated in the furnace 10.This layer may have a thickness of 10 to 20 cm, depending on factorsincluding radiative heat flux from the slag and from any electrical arcsgenerated inside the furnace 10. The temperature inside the moltenmaterial may range from 1500 to 2200 degrees Celsius, and thetemperature on the inner face of the roof 200 may range fromapproximately 1200 degrees Celsius to 1600 degrees Celsius. Accordingly,a roof 200 having a low degree of thermal and electrical conductivity issuitable for use in connection with the furnaces 10 of the presentinvention. A roof 200 that would be adapted to maintain an outer surfacetemperature of 20 to 40 degrees Celsius is especially suitable. Arelatively thick and massive roof 200 comprising materials having lowconductivity may be suitable for providing a reduced outside surfacetemperature.

As depicted, the roof 200 in accordance with an exemplary embodiment ofthe present invention may be formed of a plurality of blocks 210,adapted to fit together to form the shape of the roof 200. In theembodiment depicted in FIG. 5, all but the centremost block 212 arearc-shaped, with adjacent blocks 210 forming a series of rings, whereasthe centre block 212 is circular in shape. Skilled persons willappreciate that many other possible configurations may also be providedwithout departing from the teachings of the present invention.

As shown in FIGS. 6 and 6A, each block 210 may be made from an open cap215, formed of a non-magnetic metal, for example, copper to preventinduced current from being generated. The caps, which may be made ofcopper, may be sealed between one another by using elastic materials(e.g., rubber and teflon) between members to form an upper coppersurface of the roof. Skilled persons will appreciate that copper has ahigh thermal conductivity suitable for the intended use, but that othermaterials may also be used in accordance with the teachings of thepresent invention. In the embodiment depicted, a framework 220, whichmay be formed of rebar, for example steel rebar, supports the cap 215and a mesh network 230, which may be a steel mesh network. In especiallypreferred embodiments, this steel mesh network 230 may comprise hightemperature resistant steel.

In preferred embodiments, the cap 215 is filled with non-conductivecastable material 240, having a low degree of thermal conductivity, forexample, high alumina (Al203) castables. In general, thicker layers ofthe non-conductive and mechanically strong material will provideincreased electrical as well as thermal insulation. Castable materialsthat are non-reactive and non-soluble in water, for example high aluminacastables, tend to deteriorate more slowly during use, have a longerlifespan, and are particularly well-suited to use in the roof 200 forthe furnace 10 of the present invention. The roof 200 having arelatively increased thickness of the castable layer 240 is generallypreferred. In especially preferred embodiments, as depicted in FIG. 6,the castables 240 may exceed the depth of the cap 215 by 10 cm, 15 cm,or greater, to have an overall depth of 50 cm, 60 cm, or greater. In thepreferred embodiments depicted, the combination of the framework 220 andthe network 230 provides support for the increased mass of the layer ofcastable material 240. In use, a layer of dusts and particular matter,which may be referred to as a “skull” may accumulate on the underside ofthe roof 200, providing additional thermal insulation.

In the embodiment depicted in FIG. 5, individual roof blocks 210 aresupported vertically by a plurality of supporting members 235 which arewelded on the framework 220 and extend through appropriately sizedapertures 250 formed in the cap 215. In the embodiment depicted, eachblock 210 may be supported by four supporting members 235, eachextending through an appropriate aperture 250.

In preferred embodiments, any spaces between adjacent blocks 210 aresealed with an appropriate tar, cement, or functionally similarsubstance. Similarly, in further preferred embodiments, such spacesbetween the supporting members 235 and the cap 215, formed within theapertures 250, are sealed in a similar fashion.

In preferred embodiments, the roof 200 is adapted to support and hold alayer of cooling liquid, for example water. In these preferredembodiments, the shape of the upper surface of the roof 200 is adaptedsuch that at least some of the liquid poured or dispersed onto the roof200 will move outwardly, toward the outer edge of the roof 200. In thesepreferred embodiments, as depicted in FIG. 3, a trough 260 may be formedaround the outer radial edge of the roof 200, or at any point around theroof 200. An outer wall 275 of the trough 260 may have a higher heightthan an inner wall 270 of the trough 260, such that a layer of liquidcoolant may be retained on the roof 200 with a target thickness, forabsorbing heat from the furnace 10. In preferred embodiments, trough 260of the present invention may comprise a weir extended inner wall 270,and/or a sensor, to monitor and/or control cooling liquid depth. Infurther preferred embodiments, the cooling liquid may be displaced awayfrom the trough 260 with a liquid displacement member, for example asump pump, and may be continuously replaced by ambient or chilledcooling liquid. This displacement may be on a continuous basis, suchthat a layer of the cooling liquid is continuously refreshed and cooled,while maintaining a target depth or target depth range, which may bevaried in response to internal furnace pressure which is typicallybetween 5 mm and 10 mm of water gauge during use. In preferredembodiments, this depth of liquid coolant may be between 20 mm and 50mm.

In especially preferred embodiments, the layer of liquid coolant, whichmay be water, retained on the roof 200 may function to provide a seal toreduce the escape of gases, for example carbon monoxide, from the insidespace of the furnace 10. During use, metallurgical furnaces may generatea variety of toxic materials, including gases. By retaining a layer of atarget thickness of liquid coolant such as water on top of the roof 200,furnaces 10 may reduce the amounts of gases and dusts that pass from thefurnace 10 and into the surrounding environment, which may improveworker safety conditions and reduce environmental impact of the furnace10 operation.

Although not shown in FIG. 5, openings in the roof 200 for feed pipes,for example in the centremost block 212, may be provided as well aselsewhere as necessary. These feed pipes may be surrounded by a smallnon-magnetic member, for example a copper cylinder, which may be weldedto the plate 215, to cool the pipe and to prevent any cooling liquidfrom flowing downward along the pipe. A seal may be provided between thepipe and the copper cylinder.

In certain preferred embodiments, gas retention inside the furnace 10 isfurther aided through placing a seal (not shown), which may be anannular seal and which may have a degree of flexibility and elasticity,between the outer wall 275 of the trough 260 and the brick refractory 20to create a seal. In cases where the seal between adjacent blocks 210 iscompromised and small amounts of liquid coolant leak through, if wateris selected as liquid coolant and alumina castable material is selectedfor the blocks 210, it provides the exemplary advantage of beingnon-reactive with, and non-soluble therein. Additionally, in view of therelatively increased temperatures that such leaked liquid would beexposed to, such liquid coolant would likely vaporize. In cases wherethe integrity of the roof 200 may be compromised, steam or other visibleindication of vaporizing cooling liquid may act as a signal to stopfurnace operation and to replace any faulty aspects of the roof 200, forexample faulty blocks 210.

In certain embodiments, a roof 200 of the present invention may comprisea covering layer to enclose and prevent evaporation of liquid coolant tothe ambient environment.

A roof 200 of the present invention may be suitable for use orinstallation in conjunction with metallurgical furnaces 10 that areradially symmetric in horizontal cross-section, or furnaces that aresquare or rectangular in horizontal cross-section.

With reference to FIGS. 3 and 4, the exemplary furnace 10 may be cooledby use of air displacement means 500, which may be fans for displacingair away from an envelope of air 505 surrounding the furnace 10. In theembodiment depicted, an outer sleeve or cover 520, which may be made ofsteel, surrounds the furnace 10, and contains the envelope of air 505.The sleeve 520 may be divided into a number of sections, which maycorrespond with the number of shell sections 42, thereby surrounding,collectively with the corresponding shell section, a volume of air to bedisplaced. These sleeve sections may be welded to a flange 43 of thecorresponding shell sections 42. Each section may be provided with oneair displacement means 500. In these embodiments, the sleeve 520 willmove along with shell sections 42 during expansion and contraction ofthe furnace 10 corresponding with heating and cooling cycles. In use,the envelope of air 505, which may comprise a number of individualsegments, each contained between one segment of shell 42 and one segmentof sleeve 520, will be heated by the outer surface of the shell 40 ofthe furnace 10. The air displacement means 500, depicted as beingmounted in an air duct manifold connected to a flexible section at theupper portion of the sleeve 520, will then displace the heated air awayfrom the envelope of air 505. In the embodiment depicted, thisdisplacement will be by way of suction created by one or more fans.

As air is displaced out of the envelope 505, negative pressure may becreated within the sleeve 520. In preferred embodiments, the pressuredifferential between the envelope 505 and the outside environment issufficient to draw an adequate amount of ambient air to contribute tothe cooling of the steel shell 40, while providing the additionaladvantage of drawing away any hazardous gases which may have leaked fromthe inner furnace space 30 through the frozen skull lining and/or thoughthe refractory layers 22, 24, 26 in an unlikely event. As exemplified onFIG. 4, one or more air ingress apertures 510, which may be slots,formed in the sleeve 520 may permit an ingress of ambient or cooled airto enter the envelope 505, thereby replacing the heated displaced airand cooling the furnace 10. By use of the sleeve 520 in accordance withsome embodiments of the present invention, as compared with using onlyair displacement means or fans, the speed at which the displaced air maybe increased. In certain embodiments, the air drawn away from theenvelope 505 may be filtered or otherwise processed in order to removeor neutralize contaminants, if needed.

In further preferred embodiments, the system for cooling the furnace 10may comprise one or more spray nozzles 545, which may be any suitablespraying means, for spraying cooling liquid onto the outer surface 40 ofthe furnace 10 during use. In especially preferred embodiments, thecooling liquid is atomized into a mist by the one or more spray nozzles545 to be directed onto the outer surface 40 of the furnace 10, whichnozzles 545 may be directed accordingly in the event that hot spots inthe refractory 20 are detected through embedded thermocouples. Thecooling liquid, which may be water, is then warmed by the outer surface40 of the furnace 10 and subsequently evaporates, contributing tocooling the shell 40. When used in combination with the air displacementmeans 500 discussed above, the use of which may result in air movementalong the outer surface 520 of the furnace 10, the sprayed coolingliquid may evaporate at an enhanced rate, leading to enhanced cooling ofthe shell 40. Rapid evaporation of the cooling liquid may also have theeffect of reducing accumulation of cooling liquid, for example at alower surface of the furnace 10, and may therefore reduce associatedsafety hazards, for example explosion in the unlikely event of a furnacerunout resulting from molten metal or other materials escaping from thefurnace 10 and contacting any surplus liquid.

In preferred embodiments, a detector (not shown) may be employed forregulating spraying of cooling liquid. In use, when levels of coolingliquid are detected as having accumulated at a lower surface of envelope505, the detector would reduce the spraying of cooling liquid and/or, inthe meantime, increase the air flowrate if the hot spots are stilldetected. Once the cooling liquid has dispersed, evaporated, orotherwise been removed, such that a target level, for example none, ofcooling liquid is present at the lower surface, the spraying of coolingliquid would be increased to combat any overheat. If no hot spots aredetected, the spraying liquid may not be used.

With reference to FIGS. 7 and 8, preferred furnace 10 in accordance withexemplary aspects the present invention comprise one or more electrodes400 which are suspended into the inner furnace space 30 through openingsin the roof 200, which may be in blocks 210 that are positioned adjacentto the centremost block 212. In the embodiment depicted, the electrode400 is kept in place by a seal system for cooling the electrode 400 andproviding electrical insulation around the electrode 400. In use,typical electrodes 400 of furnace 10 of the present invention mayexperience electrical voltages of up to 1000V, and currents vary basedon the power rating and the electrode size.

The seal system depicted in FIG. 7 comprises a plurality of ceramicsealing and insulating sets of shoes 415 surrounding the electrode 400and corresponding pressing shoe members 410 radially pressing thesealing shoes 415 and the electrode 400. The sets of ceramic shoes 415may each form an L-shape, so as to be supported by a cap 460, which maybe made of a non-magnetic material, for example copper, as depicted inFIG. 7. The shoe members 410 may be made of a non-magnetic material, forexample copper. As shown in FIG. 8, each shoe member 410 is biased orforced against the sealing shoe 415 and electrode 400 by one of aplurality of biasing members 420, which may be springs. In theembodiment depicted, each pair of shoes 415 and 410 is configured tosnugly fit against the adjacent pair of 415 and 410, and is shapedappropriately to collectively form an annular ring around the electrode400. The sets of ceramic sealing shoe members 415 and pressing members410 may function as the main seal of the electrode 400, electricinsulator, as well as a cushion to accommodate the lateral movement ofthe electrode 400. The force exerted by the biasing members 420 must beadjusted so as not to reduce resistance to vertical movement of theelectrode 400.

In preferred embodiments, each biasing member 420 is supported by anon-magnetic stud 430, which may be made of copper and may be threaded.The stud 430 may be welded onto or otherwise connected to a thicknon-magnetic cooling plate 475, which may be made of copper, and thepressure of the biasing member 420 may be adjusted by a screw 450threaded through the stud 430. Above the shoes 410 and above the stud430, a cap 460, which may be constructed of non-magnetic metal, may bedisposed and supported by the studs 430. As shown in FIG. 7, inespecially preferred embodiments, threaded copper cap 460 may be screwedonto the cooling plate 475 with a thread made on the outside edge toform a seal between cap 460 and the copper cooling plate.

In certain preferred embodiments, the electrode seal is adapted to coolthe electrode 400 during use. As shown in FIG. 7, a non-magnetic plate475, which may be made of copper, may form the bottom of the electrodeseal. The ceramic sealing shoes 415 may be extended down to the bottomedge of the cooling plate 475 to completely isolate the copper plate 475from the electrode 400. A thin layer of ceramic wool material 466 may beplaced between 415 and 410 that may further extend downward to fill someor all of a possible gap between the seal shoes 415, the plate 475 andcastable 405. The plate 475 is sitting on and supported by the roofcopper cap 215 which in turn supported by the suspension rod 235. Alayer of electrical insulation material 476 may further be placedbetween the plate 475 and the cap 215.

In preferred embodiments, at the bottom of the copper cooling plate 475,the surface is covered with a layer of castable, which may be made ofhigh alumina, functioning as an electrical insulator. This insulationlayer 405 may be at least of 50 to 100 mm thick. In order to lock theinsulation layer 405, the bottom surface of the copper plate 475 may beroughened by making grooves with 10 to 20 mm deep. In preferredembodiments, conductive network 220 and framework 230 of the adjacentroof members will be covered with at least 50 to 100 mm thick of aluminacastables. During use, in an unlikely event the insulation layercastable 405 fails and an electrical bridge is formed between electrodeand copper plate 475 with condensed fumes and dusts, insulating layer476 may retain its function in isolating roof cap 215 from copper plate475.

The copper cooling plate 475 may define a channel 480 therein, throughwhich cooling liquid may be directed. In the embodiment depicted, thechannel 480 has a generally circular shape, but skilled persons willappreciate that other shapes may also provide a functional coolingchannel. In the embodiment depicted in FIG. 9, cooling liquid, forexample water, may be directed into the cooling channel 480 through aninflow member 482, be then displaced around the cooling channel 480, andflow out of the cooling channel 480 through an outflow member 484. Thecooling liquid in the cooling channel 480 may be pressurized, in orderto increase the cooling rate. In especially preferred embodiments, thiscooling liquid will, during use, flow around the cooling channel 480,thereby cooling the electrode 400, flow out of the cooling channel 480,be cooled, and then reintroduced to the cooling channel 480, all on acontinuous basis.

As depicted in FIG. 7, an opening 465 in the non-magnetic cap 460 may beincluded, to allow pressurized nitrogen (N2), or any other suitable gas,for example argon, to be directed into the seal. The pressurized gas maypenetrate through the holes in the shoes and thereby be distributedaround the electrode evenly to push down along the electrode in order tocontribute to preventing the furnace gas and dusts from within thefurnace space flowing through the gap around the electrode, in turn,thereby preventing at least some of the gas from leaking and preventingat least some substance attached to the electrode from hinderingvertical movement of the electrode.

The ceramic sealing shoes 415 may be further extended upward with anL-shape top to cover the non-magnetic cap 460. Extra high temperatureresistance packing material 467 may be packed with sealing shoes 415into a chamber 485 surrounding the electrode 400, which may function tomaintain suitable pressure of the gas limiting leaks into the furnace orinto the ambient atmosphere. This seal chamber may comprise anon-magnetic ring 462 welded on cap 460. The top of the ring 462 isthreaded to tighten the threaded cap 464. The cap has a large clearancefrom the electrode 400. In preferred embodiments, a ceramic washer 468as an electrical insulator is placed below the non-magnetic cap 464 toeven the pressure onto the packing material 467, which may act ascushion and seal. In general, electrode seals of the present inventionwill be constructed in such a way as to provide electrical insulationbetween all metals and the electrode 400. Additionally, in preferredembodiments, all electrode seal supporting materials may comprisenon-magnetic metals or alloys, in order to reduce generation of inducedcurrent. Copper is a preferred material because of its high thermalconductivity, as elements including 410, 460, and 462 may be in contactwith copper cooling plate 475 and may thereby be cooled during use.

An additional example of the bricks and steel shell arrangement for anilmenite smelting furnace in accordance with an embodiment of thepresent invention is as follows. A furnace having 50-60 MW operatingpower, with 2 layers of periclase brick (228.6 mm in thickness forthinner bricks and 406.4 mm for thicker bricks) and one layer ofgraphite brick (228.6 mm thick) comprising the refractory for thefurnace from the bottom at the skewback to the freeboard surrounded by asteel shell. The honey-comb shaped inner surface of the bricks includingthe cavities resulting from the staggered bricks with differentthickness are covered with a layer (50.8 mm) of MgO castables as asacrificial material during start-up. However, for the area in themolten iron, the cavities could be optionally filled with the castables.The steel shell internal diameter (ID) during normal furnace operation(under hot conditions) is 13,379 mm. It is expected to be contracted to13,208 mm when the furnace is fully cooled down, representing acontraction of 85 mm of refractory in radial direction. Assuming 8pieces of curved steel shell plate are used to comprise the shell, theclearance between each plate before the furnace start-up, when papersare placed between radial layers of bricks to approximate an expandedconfiguration, is estimated at 67 mm. For the innermost layer ofpericlase brick whose inner width is 101.6 mm (hottest) requires 7papers per 2 bricks with paper thickness of 0.4 mm. For the outer layerof periclase brick it requires 2 papers per brick. For the graphitebrick, it is recommended to use graphite felt as cushion. It is assumedat new installation, the graphite felt can be pressed to reduce 20% ofthe thickness at regular operating condition and during contraction tocomplete cold condition, it can be pressed to reduce 70% of itsthickness. Thus it is estimated that every two graphite bricks require 8mm thick of graphite felt without any compression. Under hot conditions,the thickness is 6.4 mm and at maximum compression it becomes 2.4 mm.

In that additional example, for the hearth refractory, expansion papersmay also be used. It is estimated that for the innermost layer 5expansion papers may be required to place around each brick. Underneaththis layer 6 expansion papers may be needed before next layer (2ndlayer) of refractory. For next layer (2nd layer) of refractory, every 3bricks as a block may require 8 papers and 2 papers may be placedbetween this layer and next layer (3rd) of refractory. No papers may berequired for bricks for the 3rd layer of refractory and between graphitebricks. At the top layer of refractory, again a sacrificial layer of MgOcastable of 50.8 mm thick is cast on the top surface of the refractory.

In that additional example, in use, in view of the refractory movementduring expansion and contraction, at the both ends of each curvedvertical shell plate a flange may be welded on the end before thestart-up. Adjacent shell segments may be bolted on the flange to fixwith the hearth flange at the bottom and at the top with a steel floor.After the bricks lined on the hearth, the shell plates may be installedand locked with a screw, bolt, or other suitable fastening means, forexample by coupling to flanges 46. Bricks 26 may then be lined againstthe shell segments, with the remaining layers 24, 22 lined againstbricks 26, to form the refractory. After bricks are laid and springs areloaded around the shell plates, the fastening means may then be removedso the plates may move freely as the furnace expands or contracts. It isestimated the hottest side temperature of the inner brick duringoperation is approximately 800-1000 degrees Celsius, and the same brickat the cold side is approximately 400 degrees Celsius. For a furnacewith an overall height of 11 m, the hot side will expand vertically by152 mm versus the cold side at approximately 84 mm. Therefore,correction may be made of the brick height to accommodate this unevenexpansion, otherwise the top brick may be tilted and the spring load onthe brick will be uneven. For example, where the brick height isdesigned at 4″ or 101.6 mm, for every 4 courses of brick, the hot sideof the brick may be shorter by 2.5 mm, i.e. a height of 68 mm forcorrection. The total number of courses of brick for the wall is 108.Correction may not be made for the top eight courses. For the next layerof brick toward the shell, the correction is similar but 3 mm with 5courses of brick. The graphite brick may not be corrected, because thetemperature is low and the linear expansion coefficient is almost zero.At the top of the sidewall bricks, a layer of Teflon™ may be laid, witha steel ring plate laid on top thereof, for direct engagement withvertical compression members which may be springs.

The description of the present invention has been presented for purposesof illustration but is not intended to be exhaustive or limited to thedisclosed embodiments. Many modifications and variations will beapparent to those of ordinary skill in the art. The embodiments werechosen to explain the principles of the invention and its practicalapplications and to enable others of ordinary skill in the art tounderstand the invention in order to implement various embodiments withvarious modifications as might be suited to other contemplated uses.

What is claimed is:
 1. A metallurgical furnace comprising: a refractory,surrounding a furnace space, for dissipating heat when the furnace spaceis heated; a force exerting member for contracting a segmented outershell around the refractory, toward the furnace space, as the refractorycontracts when the furnace space is cooling.
 2. The metallurgicalfurnace of claim 1, wherein the force exerting member allows therefractory to expand when the furnace space is heated and exerts acompressive force on the refractory as the refractory contracts when thefurnace space is cooling.
 3. The metallurgical furnace of claim 1,wherein the force exerting member comprises at least one cable disposedaround an outer surface of the segmented outer shell.
 4. Themetallurgical furnace of claim 1, wherein the force exerting membercomprises a plurality of cable pairs disposed at intervals around anouter surface of the segmented outer shell.
 5. The metallurgical furnaceof claim 1, wherein the force exerting member comprises a plurality ofpressing members disposed around an outer surface of the segmented outershell, each pressing member for pressing against an outer surface andthereby exerting a compressive force thereon.
 6. The metallurgicalfurnace of claim 5, wherein the pressing members comprise springmembers.
 7. The metallurgical furnace of claim 5, wherein the pressingmembers are adjustable to apply greater or lesser compressive force onthe segmented outer shell.
 8. The metallurgical furnace of claim 5,wherein the pressing members are biased against the outer surface of thesegmented steel shell by biasing members.
 9. The metallurgical furnaceof claim 1, additionally comprising at least one tension member mountedto the force exerting member for exerting tension on the force exertingmember, thereby exerting the force.
 10. The metallurgical furnace ofclaim 9, wherein the at least one tension member comprises a spring. 11.The metallurgical furnace of claim 9, wherein the force exerting memberis supported on at least one support member.
 12. The metallurgicalfurnace of claim 9, wherein the force exerting member is supported on aplurality of support members which are vertical columns disposed aroundthe segmented outer shell.
 13. The metallurgical furnace of claim 9,wherein the force exerting member engages at least one positioningmember, the positioning member allowing for movement of the segmentedouter shell relative to the force exerting member.
 14. The metallurgicalfurnace of claim 9, wherein the force exerting member engages at leastone positioning member, the positioning member allowing for movement ofthe segmented outer shell relative to the force exerting member, whereinthe positioning member is a wheel member pivotally mounted to thesupport member.
 15. The metallurgical furnace of claim 1, furthercomprising at least one force adjustment member connected to the forceexerting member for initially adjusting a force exerted by the forceexerting member.
 16. The metallurgical furnace of claim 3, wherein atleast one of the cables of the force exerting member has a tensionmember mounted thereto for adjusting the length of the cable, therebyadjusting the tension of the tension member and the force exerted by thecable.
 17. The metallurgical furnace of claim 16, further comprising atleast one force measuring member connected to the tension member formeasuring a tension of the tension member and thereby measuring a forceexerted by the force exerting member.
 18. The metallurgical furnace ofclaim 17, wherein the force measuring member is a dynamometer formeasuring the tension of a spring.
 19. The metallurgical furnace ofclaim 1, wherein the refractory is radially symmetric in cross-sectionat at least one point along its height.
 20. The metallurgical furnace ofclaim 19, wherein the refractory is generally round in cross-section atat least one point along the refractory's height.
 21. The metallurgicalfurnace of claim 1, wherein the segmented outer shell is generallycylindrical in shape in a contracted configuration when the furnacespace is cooled, and wherein the segmented outer shell comprises atleast one gap between horizontally adjacent shell segments in anexpanded configuration when the furnace space is heated.
 22. Themetallurgical furnace of claim 21, further comprising one or moresealing members for sealing the at least one gap between horizontallyadjacent shell segments in an expanded configuration when the furnacespace is heated.
 23. The metallurgical furnace of claim 22, wherein theone or more sealing members are strips for placement between therefractory and the segmented outer shell at a position for sealing atleast one gap between horizontally adjacent shell segments in anexpanded configuration when the furnace space is heated.
 24. Themetallurgical furnace of claim 23, wherein the refractory comprises aninnermost layer of thermally conductive bricks disposed around thefurnace space for absorbing and dissipating the heat.
 25. Themetallurgical furnace of claim 24, wherein the refractory furthercomprises at least one additional layer of thermally conductive bricksdisposed around the innermost layer of thermally conductive bricks, forfurther absorbing and dissipating the heat.
 26. The metallurgicalfurnace of claim 25, wherein the additional layer comprises brickscomprising a different material than bricks of innermost layer.
 27. Themetallurgical furnace of claim 24, wherein at least some of thethermally conductive bricks comprise periclase.
 28. The metallurgicalfurnace of claim 24, wherein the refractory further comprises anoutermost layer of bricks disposed around the one or more layers ofthermally conductive bricks.
 29. The metallurgical furnace of claim 28,wherein the outer layer of bricks comprises a graphite material.
 30. Themetallurgical furnace of claim 29, wherein the refractory, prior to thefurnace space being initially heated, comprises at least one layer ofspacer material between the innermost and the least one additional layerof thermally conductive bricks, thereby resulting in a refractorydiameter larger than a contracted configuration of the shell, andwherein the spacer material is made of a material adapted to combust ordissipate when the furnace space is heated, thereby leaving space tocompensate for additional space occupied by expanding thermallyconductive bricks.
 31. The metallurgical furnace of claim 1, wherein thesegmented outer shell comprises at least three segments.
 32. Themetallurgical furnace of claim 1, wherein the segmented outer shellcomprises a smaller or larger number of segments proportionate with therelative size of the furnace.
 33. The metallurgical furnace of claim 32,wherein the segmented outer shell comprises at least eight segments. 34.The metallurgical furnace of claim 1, wherein each segment of thesegmented outer shell comprises an edge which is adapted to cooperatewith an edge of an adjacent shell segment.
 35. The metallurgical furnaceof claim 1, further comprising one or more sealing members for placementbetween the segmented outer shell and the refractory, each sealingmember for sealing one or more gaps formed between horizontally adjacentshell segments in an expanded configuration when the furnace space isheated.
 36. The metallurgical furnace of claim 1, further comprising oneor more retaining members for movably connecting pairs of horizontallyadjacent shell segments, each retaining member thereby providing amaximum gap distance between each connected pair of horizontallyadjacent shell segments.